Height adjustment mechanisms for controlling the height of a chair are well known. Typically, such mechanisms actuate a gas cylinder on which a chair is supported. Conventional gas cylinders have two chambers separated by a normally closed valve. Protruding from one end of the gas cylinder is a valve-opening button, or finger, that when depressed causes the valve separating the two gas cylinder chambers to open, thereby allowing the cylinder to extend or retract in order to adjust the height of the chair.
Known actuation mechanisms for actuating the valve-opening member typically consist of a rod that is tiltably mounted above the valve-opening finger. The rod typically terminates in a handle which is accessible by the user. With this type of actuation mechanism, the user may raise the handle, thereby causing the rod to tilt downward and depress the valve-opening finger. An example of such an actuation mechanism is described in U.S. Pat. No. 6,290,296 to Beggs.
A common problem that exists with the above-described actuation mechanisms is that they have relatively large space requirements to accommodate the rod inside the housing assembly, and to allow the rod to be tilted. This requires the housing assembly in which the rod resides to be relatively large. Large and bulky housing assemblies detract from the aesthetic appearance of chairs.
One proposed solution to the aforesaid problems is described by U.S. Pat. No. 6,213,552 to Miotto. There, the height adjustment mechanism consists of a slider element motivated by a user actuatable handle. The slider may be pushed inwardly against an upstanding arm of a pivoting member. This causes the pivoting member to pivot so that a second arm of the pivoting member depresses the valve control finger. A drawback of the mechanism described in Miotto is that it is relatively complex.
It would therefore be desirable to have a height adjustment mechanism for a chair that is simple in design, does not unduly detract from the aesthetic appeal of the chair, and whose physical dimensions are relatively small.